Method of forming topology-controlled amorphous carbon polymer film

ABSTRACT

A method of forming a topology-controlled layer on a patterned recess of a substrate, includes: (i) depositing a Si-free C-containing film having filling capability on the patterned recess of the substrate by pulse plasma-assisted deposition to fill the recess in a bottom-up manner or bottomless manner; and (ii) subjecting the bottom-up or bottomless film filled in the recess to plasma aching to remove a top portion of the filled film in a manner leaving primarily or substantially only a bottom portion of the filled film or primarily or substantially only a sidewall portion of the filled film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/876,588, filed on Jul. 19, 2019, in the United States Patent andTrademark Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method of forming atopology-controlled amorphous carbon film on a patterned recess of asubstrate.

Description of the Related Art

In processes of fabricating integrated circuits such as those forshallow trench isolation, inter-metal dielectric layers, passivationlayers, etc., it is often necessary to fill trenches (any recesstypically having an aspect ratio of one or higher) with insulatingmaterial. However, with miniaturization of wiring pitch of large scaleintegration (LSI) devices, void-free filling of high aspect ratio spaces(e.g., AR≥3) becomes increasingly difficult due to limitations ofexisting deposition processes.

In view of the above, the present inventor developed a gap-filltechnology for deposition of flowable film and disclosed the technologyin U.S. patent application Ser. No. 16/026,711, filed Jul. 3, 2018,which provides complete gap-filling by plasma-assisted deposition usinga hydrocarbon precursor substantially without formation of voids underconditions where a nitrogen, oxygen, or hydrogen plasma is not required,the disclosure of which is herein incorporated by reference in itsentirety.

However, if a certain application, where a sacrificial etch stop layeror protection layer, for example, is necessary only at the bottom of arecess, requires bottom-only deposition of amorphous carbon using theabove gap-fill technology in trenches of a substrate, there might be thefollowing issues: i) a certain amount of film (although it is small butnot negligible) may be deposited on the top face of the substrate; ii)the amount of film deposited at the bottom of each trench may beirregular depending on the structure volume of each trench (see (a) ofFIG. 8); and iii) even when the structure volume of each trench issimilar, there may be some randomness in gap-filling (see (b) of FIG.8). The present inventor provides herein a solution to the above issues.

In other applications such as 3D NAND flash, ultradeep hole straightetching is required. However, it is very difficult to maintain thestraight structure as is due to the occurrence of sidewall etchingduring the hole etching, resulting in lowering CD integrity. The presentinventor has discovered that the above gap-fill technology can provide asolution to the above problem.

Any discussion of problems and solutions involved in the related art hasbeen included in this disclosure solely for the purposes of providing acontext for the present invention, and should not be taken as anadmission that any or all of the discussion were known at the time theinvention was made.

SUMMARY OF THE INVENTION

In view of the above, some embodiments provide a method of forming atopology-controlled layer on a patterned recess of a substrate,comprising: (i) depositing a Si-free C-containing film having fillingcapability on the patterned recess of the substrate by pulseplasma-assisted deposition to fill the recess in a bottom-up manner orbottomless manner; and (ii) subjecting the bottom-up or bottomless filmfilled in the recess to plasma ashing to remove a top portion of thefilled film in a manner leaving primarily only a bottom portion of thefilled film or primarily only a sidewall portion of the filled film.According to the above embodiments, by using the gap-fill technology,the topology of the film can be manipulated. The degree of flowabilityof film relative to the size of the trench can primarily determinewhether deposition is bottom-up deposition or bottomless deposition.

When the flowability of film is sufficiently high relative to targettrenches, bottom-up deposition occurs, and after completely filling thetrenches and further depositing film above the trenches, by subjectingthe film to plasma ashing, the top portion of the film above thetrenches as well as an upper portion of film filled in the trenches canequally be removed to a uniform depth of the trenches so as to obtaintrenches filled with film having substantially a uniform depth.

When the flowability of film is sufficiently low relative to targettrenches, bottomless deposition occurs; however, because the film isflowable, even when the film does not reach the bottom of the trench andcloses the upper opening of the trench, the film can deposit along thesidewall of the trench to cover the sidewall to a certain depth from thetop surface of the substrate. After completion of deposition of thefilm, by subjecting the film to plasma ashing, the portion of the filmclosing the opening of the trench can be removed to open the trench,leaving the sidewall film as a spacer. Thereafter, ultradeep holestraight etching can be performed. Since the bottom of the trench issubstantially not covered by the film, and the sidewall film can protectthe sidewall from being etched during the ultradeep hole straightetching, etching can progress in the depth direction to form anultradeep straight hole, without degrading CD integrity.

For purposes of summarizing aspects of the invention and the advantagesachieved over the related art, certain objects and advantages of theinvention are described in this disclosure. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described withreference to the drawings of preferred embodiments which are intended toillustrate and not to limit the invention. The drawings are greatlysimplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of a PEALD (plasma-enhanced atomiclayer deposition) apparatus for depositing a dielectric film usable inan embodiment of the present invention.

FIG. 1B illustrates a schematic representation of a precursor supplysystem using a flow-pass system (FPS) usable in an embodiment of thepresent invention.

FIG. 2 is a chart illustrating schematic cross sectional views oftrenches subjected to bottom-up deposition ((a)→(b)→(c)), and bottomlessdeposition ((a)→(d)→(e)) according to embodiments of the presentinvention.

FIG. 3 shows STEM photographs of cross-sectional views of trenchessubjected to bottom-up deposition in (a), followed by O₂/Ar ashing in(b) or by N₂/H₂ ashing in (c) according to embodiments of the presentinvention.

FIG. 4 shows a schematic illustration of a STEM photograph of across-sectional view of a trench subjected to bottomless deposition (300cycles) without ashing

FIG. 5 shows a schematic illustration of a STEM photographs of across-sectional view of a trench subjected to bottomless deposition (300cycles), followed by ashing (90 seconds) according to an embodiment ofthe present invention.

FIG. 6 shows a schematic illustration of a STEM photograph of across-sectional view of a trench subjected to bottomless deposition (350cycles) without ashing.

FIG. 7 shows a schematic illustration of a STEM photograph of across-sectional view of a trench subjected to bottomless deposition (350cycles), followed by ashing (90 seconds) according to an embodiment ofthe present invention.

FIG. 8 shows STEM photographs of cross-sectional views of trenchessubjected to bottom-up deposition, wherein (a) represents trencheshaving different widths, and (b) represents trenches filled withirregular amount of film.

FIG. 9 shows STEM photographs of cross-sectional views of trenchessubjected to bottom-up deposition, wherein (a) represents trenches atcompletion of deposition, and (b) represents the trenches after ashingaccording to an embodiment of the present invention.

FIG. 10 shows STEM photographs of cross-sectional views of trenchessubjected to bottom-up deposition (full fill), wherein raw (a)represents a mixture of wide trenches and narrow trenches havingdifferent widths (the scale represents 300 nm), raw (b) representsintermediate trenches (the scale represents 60 nm), and raw (c)represents wide trenches with slight difference in width (the scalerepresents 60 nm), column (1) represents the trenches with full-filldeposition (210 cycles of deposition) prior to ashing, column (2)represents the trenches after ashing for 105 seconds, column (3)represents the trenches after ashing for 129 seconds, and column (4)represents the trenches after ashing for 165 seconds, according to anembodiment of the present invention.

FIG. 11 shows STEM photographs of cross-sectional views of trenchessubjected to bottom-up deposition, wherein (a) represents trenches atcompletion of full-fill deposition (210 cycles of deposition), (b)represents the trenches after ashing for 240 seconds, and (c) representsthe trenches after ashing for 300 seconds, according to an embodiment ofthe present invention.

FIG. 12 is a chart illustrating the sequence of processes of filmformation according to an embodiment of the present invention, wherein acell in gray represents an ON state whereas a cell in white representsan OFF state, and the width of each column does not represent durationof each process.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid andmay be constituted by a single gas or a mixture of gases, depending onthe context. Likewise, an article “a” or “an” refers to a species or agenus including multiple species, depending on the context. In thisdisclosure, a process gas introduced to a reaction chamber through ashowerhead may be comprised of, consist essentially of, or consist of asilicon-free hydrocarbon precursor and an additive gas. The additive gasmay include a plasma-generating gas for exciting the precursor to forman amorphous carbon polymer when RF power is applied to the additivegas. The additive gas may be an inert gas which may be fed to a reactionchamber as a carrier gas and/or a dilution gas. The additive gas maycontain no reactant gas for oxidizing or nitriding the precursor.Alternatively, the additive gas may contain a reactant gas for oxidizingor nitriding the precursor to the extent not interfering with plasmapolymerization forming an amorphous carbon-based polymer. Further, insome embodiments, the additive gas contains only a plasma-generating gas(e.g., noble gas). The precursor and the additive gas can be introducedas a mixed gas or separately to a reaction space. The precursor can beintroduced with a carrier gas such as a rare gas. A gas other than theprocess gas, i.e., a gas introduced without passing through theshowerhead, may be used for, e.g., sealing the reaction space, whichincludes a seal gas such as a rare gas. In some embodiments, the term“precursor” refers generally to a compound that participates in thechemical reaction that produces another compound, and particularly to acompound that constitutes a film matrix or a main skeleton of a film,whereas the term “reactant” refers to a compound, other than precursors,that activates a precursor, modifies a precursor, or catalyzes areaction of a precursor, wherein the reactant may provide an element(such as O, C, N) to a film matrix and become a part of the film matrix,when in an excited state. The term “plasma-generating gas” refers to acompound, other than precursors and reactants, that generates a plasmawhen being exposed to electromagnetic energy, wherein theplasma-generating gas may not provide an element (such as O, C, N) to afilm matrix which becomes a part of the film matrix. The term“plasma-aching gas” refers to a gas which ashes a film when in a stateexcited either directly (direct plasma) or remotely (remote plasma). Insome embodiments, the “plasma-aching gas” is a single gas or a mixed gasof two or more gases. The term “aching” refers to removal of organicmatter using a plasma, leaving mineral components behind as a residue(ash) which is typically removed with a vacuum pump.

In some embodiments, “film” refers to a layer continuously extending ina direction perpendicular to a thickness direction substantially withoutpinholes to cover an entire target or concerned surface, or simply alayer covering a target or concerned surface. In some embodiments,“layer” refers to a structure having a certain thickness formed on asurface or a synonym of film or a non-film structure. A film or layermay be constituted by a discrete single film or layer having certaincharacteristics or multiple films or layers, and a boundary betweenadjacent films or layers may or may not be clear and may be establishedbased on physical, chemical, and/or any other characteristics, formationprocesses or sequence, and/or functions or purposes of the adjacentfilms or layers. Further, in this disclosure, any two numbers of avariable can constitute a workable range of the variable as the workablerange can be determined based on routine work, and any ranges indicatedmay include or exclude the endpoints. Additionally, any values ofvariables indicated (regardless of whether they are indicated with“about” or not) may refer to precise values or approximate values andinclude equivalents, and may refer to average, median, representative,majority, etc. in some embodiments. Further, in this disclosure, theterms “constituted by” and “having” refer independently to “typically orbroadly comprising”, “comprising”, “consisting essentially of”, or“consisting of” in some embodiments. In this disclosure, any definedmeanings do not necessarily exclude ordinary and customary meanings insome embodiments.

In this disclosure, “continuously” refers to without breaking a vacuum,without interruption as a timeline, without any material interveningstep, without changing treatment conditions, immediately thereafter, asa next step, or without an intervening discrete physical or chemicalstructure between two structures other than the two structures in someembodiments.

In this disclosure, the term “filling capability” (also referred to as“flowability”) refers to a capability of filling a gap substantiallywithout voids (e.g., no void having a size of approximately 5 nm orgreater in diameter) and seams (e.g., no seam having a length ofapproximately 5 nm or greater), wherein seamless/voidless bottom-upgrowth of a layer is observed, when a film is deposited in a wide trenchhaving an aspect ratio of about 1 or more.

The flowability is often manifested as a concave surface of a film at abottom of a wide trench before filling the trench, and also manifestedas a substantially planar top surface of a film when being continuouslydeposited after completely filling the trench (planarization). Suchdeposition is referred to as “bottom-up deposition.”

When a trench is narrow and deep, even though a film is flowable, thefilm may not reach a bottom of the trench. In that case, the flowabilityis often manifested as a roughly or substantially conformal film alongsidewalls of the trench with substantially no film at a bottom of thetrench and typically with a top opening of the trench closed off by afilm. Since the film is flowable, the sidewall film flows and extendsdownward along the sidewalls, thereby forming a thin film, wherein aratio of averaged thickness of a substantially conformal part of thefilm (except a top part closing the top opening of the trench, which issubsequently removed by aching) to depth of the film in the trench(length extended toward the bottom along the sidewall) may be in a rangeof 0.1% to 10% (typically 0.5% to 5%). Such deposition is referred to as“bottomless deposition”.

In this disclosure, a recess between adjacent protruding structures andany other recess pattern is referred to as a “trench”. That is, a trenchis any recess pattern including a hole/via. For bottom-up deposition, insome embodiments, the trench has a width of about 20 nm to about 100 nm(typically about 30 nm to about 50 nm) (wherein when the trench has alength substantially the same as the width, it is referred to as ahole/via), a depth of about 30 nm to about 100 nm (typically about 40 nmto about 60 nm), and an aspect ratio of about 2 to about 10 (typicallyabout 2 to about 5). For bottomless deposition, in some embodiments, thetrench has a width (CD) of about 5.5 nm to about 200 nm (typically about10 nm to about 100 nm), a depth of about 800 nm to about 10,000 nm(typically about 300 nm to about 8,000 nm), and an aspect ratio of about15 to about 150 (typically about 20 to about 100). Proper dimensions ofthe trench may vary depending on the process conditions, flowability ofthe film, film compositions, intended applications, etc. By tuning theflowability of the film, for example, bottom-up deposition andbottomless deposition can be realized in trenches having sizes differentfrom those described above.

In this disclosure, the term “substantially no deposition,”“substantially no film,” or the like refers to a quantity functionallyequivalent to zero, an immaterial or negligible quantity, a quantitywhich does not materially interfere with subsequent processes (e.g.,ashing), a quantity lower than a detectable or observable quantity, orthe like.

In this disclosure, any defined meanings do not necessarily excludeordinary and customary meanings in some embodiments. Also, in thisdisclosure, “the invention” or “the present invention” refers to atleast one of the embodiments or aspects explicitly, necessarily, orinherently disclosed herein.

Embodiments will be explained with respect to preferred embodiments.However, the present invention is not intended to be limited to thepreferred embodiments.

Some embodiments provide a method of forming a topology-controlled layeron a patterned recess of a substrate, comprising: (i) depositing aSi-free C-containing film having filling capability on the patternedrecess of the substrate by pulse plasma-assisted deposition to fill therecess in a bottom-up manner or bottomless manner; and (ii) subjectingthe bottom-up or bottomless film filled in the recess to plasma ashingto remove a top portion of the filled film in a manner leaving primarilyonly a bottom portion of the filled film or primarily only a sidewallportion of the filled film. The Si-free C-containing film may typicallybe an amorphous carbon polymer film which is a flowable film. When anamorphous carbon polymer film is formed by using a plasma-assistedmethod, the resultant amorphous carbon polymer film is constituted byhydrogenated amorphous carbon polymer. In this disclosure, ahydrogenated amorphous carbon polymer may simply refer to an amorphouscarbon polymer, which may also be referred to as “aC:H” or simply “aC”as an abbreviation. Further, in this disclosure, SiC, SiCO, SiCN, SiCON,or the like is an abbreviation indicating a film type (indicated simplyby primary constituent elements) in a non-stoichiometric manner unlessdescribed otherwise.

In some embodiments, in step (i), the Si-free C-containing film isdeposited using a hydrocarbon precursor. In some embodiments, step (i)comprises: (ia) supplying a precursor to a reaction space where thesubstrate is placed, and (ib) exposing the patterned recess of thesubstrate to a plasma to deposit the Si-free C-containing film in thepatterned recess, wherein step (ib) is conducted intermittently in amanner pulsing the plasma, and step (ia) is conducted continuously orintermittently without overlapping step (ib) as a step prerequisite forstep (ib). In some embodiments, the Si-free C-containing film isconstituted substantially by hydrocarbons.

Deposition of flowable film is known in the art; however, conventionaldeposition of flowable film uses chemical vapor deposition (CVD) withconstant application of RF power, since pulse plasma-assisted depositionsuch as PEALD is well known for depositing a conformal film which is afilm having characteristics entirely opposite to those of flowable film.In some embodiments, flowable film is a silicon-free carbon-containingfilm constituted by an amorphous carbon polymer, and although anysuitable one or more of hydrocarbon precursors can be candidates, insome embodiments, the precursor includes an unsaturated or cyclichydrocarbon having a vapor pressure of 1,000 Pa or higher at 25° C. Insome embodiments, the precursor is at least one selected from the groupconsisting of C2-C8 alkynes (C_(n)H_(2n-2)), C2-C8 alkenes(C_(n)H_(2n)), C2-C8 diene (C_(n)H₂), C3-C8 cycloalkenes, C3-C8annulenes (C_(n)H_(n)), C3-C8 cycloalkanes, and substituted hydrocarbonsof the foregoing. In some embodiments, the precursor is ethylene,acetylene, propene, butadiene, pentene, cyclopentene, benzene, styrene,toluene, cyclohexene, and/or cyclohexane.

In some embodiments, as the gap-fill technology for deposition offlowable film, the method disclosed in U.S. patent application Ser. No.16/026,711 can be used, which provides complete gap-filling byplasma-assisted deposition using a hydrocarbon precursor substantiallywithout formation of voids under conditions where a nitrogen, oxygen, orhydrogen plasma is not required, the disclosure of which is hereinincorporated by reference in its entirety.

By changing deposition conditions or process parameters, a non-flowablefilm can be formed. For example, such parameters include, but are notlimited to, partial pressure of precursor, deposition temperature,deposition pressure, etc. For example, by increasing the depositiontemperature, decreasing the deposition pressure, and/or decreasing theprecursor ratio (a ratio of precursor flow to carrier/dilution gasflow), the flowability of film becomes low. In some embodiments, process(i) (deposition process) is conducted by plasma-enhanced atomic layerdeposition (PEALD) or other cyclic plasma-assisted deposition (e.g.,cyclic PECVD). As a plasma, a capacitively coupled plasma, inductivelycoupled plasma, remote plasma, a plasma generated by RF power, a plasmagenerated by microwaves, etc. can be used.

In some embodiments, the plasma aching in step (ii) is conducted using adirect or remote oxygen or hydrogen plasma. In some embodiments, thedirect or remote oxygen or hydrogen plasma is a direct or remote plasmaof gas(es) selected from the group consisting of solely Hz, a mixture ofAr and H₂ (an Ar/H₂ flow ratio of 0.005 to 0.995, typically 0.05 to0.75), a mixture of He and H₂ (a He/H₂ flow ratio of 0.005 to 0.995,typically 0.05 to 0.75), a mixture of N₂ and H₂ (an N₂/H₂ flow ratio of0.005 to 0.995, typically 0.05 to 0.75), solely O₂, a mixture of O₂ andAr (an O₂/Ar flow ratio of 0.005 to 0.995, typically 0.05 to 0.75), amixture of O₂ and He (an O₂/He flow ratio of 0.005 to 0.995, typically0.05 to 0.75), and a mixture of O₂ and N₂ (an O₂/N₂ flow ratio of 0.005to 0.995, typically 0.05 to 0.75).

In some embodiments, an aspect ratio of the recess is in a range of 10to 150 (typically 15 to 100), and a depth of the recess is more than 200nm wherein the recess is filled with the film in a bottomless manner instep (i) and a top portion of the filled film closes off a top openingof the recess. In some embodiments, plasma ashing is conducted to openthe closed top portion of the recess and to leave primarily orsubstantially only the sidewall portion of the filled film in step (ii).

In some embodiments, the substrate has multiple recesses having aspectratios of 2 to 30 (typically 3 to 20), wherein the recesses are filledwith the film in a bottom-up manner in step (i) wherein there arevariations in surface topology due to the loading effect. In someembodiments, step (i) continues until planarization of the film abovethe multiple recesses occurs, and plasma ashing is then conducted tomake the surface topology of the film filled in the multiple recessesuniform, and to leave primarily or substantially only the bottom portionof the filled film in step (ii).

Embodiments will be explained with respect to the drawings. However, thepresent invention is not intended to be limited to the drawings.

FIG. 2 is a chart illustrating schematic cross sectional views oftrenches subjected to bottom-up deposition ((a)→(b)→(c)), and bottomlessdeposition ((a)→(d)→(e)) according to embodiments of the presentinvention. First, in (a) of FIG. 2, a substrate with trenches isprovided, wherein for bottom-up deposition, a substrate 21 has a trench20 having a width which is sufficiently wide to allow a flowable film toflow into the trench, and having a depth which is sufficiently small toallow the flowable film to reach a bottom of the trench 20, whereas forbottomless deposition, a substrate 31 has a trench 30 having a widthwhich is sufficiently wide to allow a flowable film to flow into thetrench but sufficiently narrow to clog the top opening of the trench 30with the film before the film reaches a bottom of the trench 30, andhaving a depth which is sufficiently large to disallow the flowable filmto reach a bottom of the trench 30. Suitable sizes of trenches, by wayof example, are described in this disclosure and can be selectedaccording to the flowability of the film, for example. It should benoted that FIG. 2 is overly simplified and is not scaled.

Next, in the deposition process, the same process conditions ofdeposition can be used for both bottom-up deposition in (b) andbottomless deposition in (d), except for the number of depositioncycles, the duration of ashing, etc. which are modified depending on thesize of trenches, the target deposition thickness of the film, thetarget ashing quantity, the target final topology of the film, etc. In(b), the flowable film fills the trench 20 in a bottom-up manner andcontinuously deposits on the substrate 21 after completely filling thetrench 20, until a top surface of the film 22 is planarized.Planarization can be achieved due to the flowability of the film. In(d), the flowable film deposits on a top of the substrate 31 and flowsinto the trench 30, moving downward along sidewalls of the trench 30 ina bottomless manner, while clogging the top opening of the trench 30with the flowable film 32. Since the flowable film flows downward alongthe sidewall of the trench 30 having an aspect ratio of about 10 to 100,for example, the film on the sidewall becomes substantially conformalalong the sidewall, which can serve as a spacer. It should be noted thatthe bottom-up deposition and the bottomless deposition can be conductedon trenches having the same size, by tuning the flowability of film foreach deposition. For example, the method of tuning the flowabilitydisclosed in U.S. patent application Ser. No. 16/026,711 can be used.

Next, in the aching process, the amorphous carbon constituting the filmis removed (ached) from the top surface exposed to a plasma to a depthsuitable for bottom-only topology or sidewall-only topology. In (c), byremoving the portion of the film 22 deposited on the top surface of thesubstrate 21 and an upper portion of the film 22 filled in the trench 20in a bottom-up manner, a film 23 having bottom-only topology can beobtained, which is homogenous and has substantially a uniform depth. In(e), by removing the portion of the film 32 deposited on the top surfaceof the substrate 31 and an upper portion of the film 32 closing theupper opening of the trench 30 in a bottomless manner, a film 33 havingsidewall-only topology can be obtained, which is homogenous and hassubstantially a uniform thickness.

In some embodiments, preferably, the deposition process uses ALD-likerecipes (e.g., feed/purge/plasma strike/purge) wherein the purge afterfeed is voluntarily severely shortened to leave high partial pressure ofprecursor during the plasma strike, as disclosed in U.S. patentapplication Ser. No. 16/026,711. This is clearly distinguished from ALDchemistry or mechanism. The above processes can be based on pulse plasmaCVD which also imparts good filling capabilities to resultant filmsalthough the ALD-like recipes may be more beneficial as discussed later.

In some embodiments, the critical aspects for flowability of depositingfilm, different from conventional ALD, include:

1) High-enough partial pressure during the entire RF-ON period forpolymerization/chain growth to progress;

2) Sufficient energy to activate the reaction (defined by the RF-ONperiod and RF power), a not overly long RF-ON period; and

3) Temperature and pressure for polymerization/chain growth set above amelting point of flowable phase but below a boiling point of thedeposited material.

In some embodiments, process parameter ranges are adjusted as followsfor tuning the flowability of film:

TABLE 1 (numbers are approximate) Low ← Viscosity → High Partialpressure of precursor (Pa) >50 (preferably, >200) Wafer temperature (°C.) −10 to 200 (preferably, 50 to 150) Total pressure (Pa) 300 to 101325(preferably, >500)

As for pressure, high pressure is preferable for flowability, sincegravity and surface tension are the driving force for the film to flowat the bottom. As for temperature, low temperature is preferable forflowability (this is much less intuitive), although high temperaturefavors the polymer chain growth rate.

FIG. 12 is a chart illustrating the sequence of processes of filmformation according to an embodiment of the present invention, wherein acell in gray represents an ON state whereas a cell in white representsan OFF state, and the width of each column does not represent durationof each process. This simplified process sequence can be adopted to bothbottom-up deposition and bottomless deposition, and in some embodiments,the same process conditions of deposition can be used for both bottom-updeposition and bottomless deposition, except for the number ofdeposition cycles, the duration of ashing, etc. which are modifieddepending on the size of trenches, the target deposition thickness ofthe film, the target ashing quantity, the target final topology of thefilm, etc.

This process sequence comprises a deposition process (“Feed” →“Purge”→“RF Pulse-1” (plasma polymerization)→“Purge”), and a plasma ashingprocess (“Stabilize” →“RF Pulse-2” (plasma ashing)→“Purge”). The plasmapolymerization process comprises depositing an amorphous carbon polymerfilm on a substrate having trenches by PEALD-like deposition using a Si-and metal-free, C-containing precursor and a plasma-generating gas whichgenerates a plasma by applying RF power (RF) between two electrodesbetween which the substrate is placed in parallel to the two electrodes,wherein RF power is applied in each sublayer deposition cycle ofPEALD-like deposition, wherein the plasma-generating gas and the carriergas flow continuously and function also as a purging gas during “Purge”after “Feed” and during “Purge” after “RF Pulse-1”.

In some embodiments, the feed time is in a range of 0.3 to 10 seconds(typically 0.6 to 2 seconds), the purge time after the feed is in arange of 0 to 0.5 seconds (typically 0 to 0.3 seconds), the RF time isin a range of 0.5 to 2 seconds (typically 0.8 to 1.5 seconds), the purgetime after the RF is in a range of 0 to 0.5 seconds (typically 0 to 0.1seconds), the carrier gas flow is in a range of 0 to 0.8 slm (typically0.1 to 0.3 slm), the plasma-generating gas flow is in a range of 0 to0.5 slm (typically 0.1 to 0.3 slm), and the RF power is in a range of 50to 400 W (typically 75 to 200 W) for a 300-mm wafer (for different sizewafers, the above wattage is applied as W per unit area (cm²) of eachwafer).

The flowability of film is temporarily obtained when a volatilehydrocarbon precursor, for example, is polymerized by a plasma anddeposited on a surface of a substrate, wherein gaseous monomer(precursor) is activated or fragmented by energy provided by plasma gasdischarge so as to initiate polymerization, and when the resultantpolymer material is deposited on the surface of the substrate, thematerial shows temporarily flowable behavior. When the deposition stepis complete, the flowable film is no longer flowable but is solidified,and thus, a separate solidification process is not required.

The deposition process is a PEALD-like process, one cycle of which forforming a sublayer (typically thicker than a monolayer) may be repeatedat q times until a desired thickness of the amorphous carbon polymerfilm is obtained before starting the plasma ashing process, wherein q isan integer of 5 to 100 (preferably 25 to 50) for the bottom-updeposition, depending on the size of the trenches, the intended use ofthe film, etc., so as to deposit the amorphous carbon polymer filmhaving a thickness of 2.5 nm to 50 nm (preferably 7.5 nm to 25 nm) abovethe top surface of the substrate before starting the plasma ashingprocess; and wherein q is an integer of 10 to 200 (preferably 40 to 100)for the bottomless deposition, depending on the size of the trenches,the intended use of the film, etc., so as to deposit the amorphouscarbon polymer film having a thickness of 5 nm to 100 nm (preferably 20nm to 50 nm) above the top surface of the substrate before starting theplasma ashing process.

Next, the plasma ashing process begins, which comprises feeding anashing gas (H₂ or O₂, or a mixture of the foregoing and N₂, Ar, and/orHe) to the reaction space (“Stabilize”) which is excited by RF power(RF) to generate a plasma and ash the amorphous carbon polymer film (“RFPulse-2”), followed by purging (“Purge”), wherein the ashing gas is fedcontinuously to the reaction space throughout the plasma ashing process.In some embodiments, the RF power for the plasma ashing is in a range of50 to 500 W (typically 50 to 200 W) under a pressure of 100 Pa to 1000Pa (typically 200 to 600 Pa) for a duration of 5 to 200 seconds(typically 10 to 100 seconds), the stabilization time is in a range of 5to 60 seconds (typically 10 to 30 seconds), the purge time after the RFis in a range of 5 to 60 seconds (typically 10 to 30 seconds), and theashing gas flow is in a range of 0.1 to 10 slm (typically 0.5 to 2 slm).

In some embodiments, throughout the entirety of the processes, thecarrier gas is fed continuously to the reaction space in a range of 0sccm to 2000 sccm (preferably 100 sccm to 500 sccm), for example. Also,the temperature of the processes may be in a range of −50° C. to 175° C.(preferably 35° C. to 150° C.).

The plasma-generating gas in the deposition process and the ashing gasin the plasma ashing process can be the same or different, e.g., bothcan be Ar and/or He.

The continuous flow of the carrier gas can be accomplished using aflow-pass system (FPS) wherein a carrier gas line is provided with adetour line having a precursor reservoir (bottle), and the main line andthe detour line are switched, wherein when only a carrier gas isintended to be fed to a reaction chamber, the detour line is closed,whereas when both the carrier gas and a precursor gas are intended to befed to the reaction chamber, the main line is closed and the carrier gasflows through the detour line and flows out from the bottle togetherwith the precursor gas. In this way, the carrier gas can continuouslyflow into the reaction chamber, and can carry the precursor gas inpulses by switching between the main line and the detour line. FIG. 1Billustrates a precursor supply system using a flow-pass system (FPS)according to an embodiment of the present invention (black valvesindicate that the valves are closed). As shown in (a) in FIG. 1B, whenfeeding a precursor to a reaction chamber (not shown), first, a carriergas such as Ar (or He) flows through a gas line with valves b and c, andthen enters a bottle (reservoir) 26. The carrier gas flows out from thebottle 26 while carrying a precursor gas in an amount corresponding to avapor pressure inside the bottle 26, and flows through a gas line withvalves f and e, and is then fed to the reaction chamber together withthe precursor. In the above, valves a and d are closed. When feedingonly the carrier gas (noble gas) to the reaction chamber, as shown in(b) in FIG. 1B, the carrier gas flows through the gas line with thevalve a while bypassing the bottle 26. In the above, valves b, c, d, e,and f are closed.

The process cycle can be performed using any suitable apparatusincluding an apparatus illustrated in FIG. 1A, for example. FIG. 1A is aschematic view of a PEALD apparatus, desirably in conjunction withcontrols programmed to conduct the sequences described below, usable insome embodiments of the present invention. In this figure, by providinga pair of electrically conductive flat-plate electrodes 4, 2 in paralleland facing each other in the interior 11 (reaction zone) of a reactionchamber 3, applying HRF power (13.56 MHz or 27 MHz) 25 to one side, andelectrically grounding the other side 12, a plasma is excited betweenthe electrodes. A temperature regulator is provided in a lower stage 2(the lower electrode), and a temperature of a substrate 1 placed thereonis kept constant at a given temperature. The upper electrode 4 serves asa shower plate as well, and reactant gas and/or dilution gas, if any,and precursor gas are introduced into the reaction chamber 3 through agas line 27 and a gas line 28, respectively, and through the showerplate 4. Additionally, in the reaction chamber 3, a circular duct 13with an exhaust line 7 is provided, through which gas in the interior 11of the reaction chamber 3 is exhausted. Additionally, a transfer chamber5 disposed below the reaction chamber 3 is provided with a seal gas line24 to introduce seal gas into the interior 11 of the reaction chamber 3via the interior 16 (transfer zone) of the transfer chamber 5 wherein aseparation plate 14 for separating the reaction zone and the transferzone is provided (a gate valve through which a wafer is transferred intoor from the transfer chamber 5 is omitted from this figure). Thetransfer chamber is also provided with an exhaust line 6. In someembodiments, the deposition of multi-element film and surface treatmentare performed in the same reaction space, so that all the steps cancontinuously be conducted without exposing the substrate to air or otheroxygen-containing atmosphere.

In some embodiments, in the apparatus depicted in FIG. 1A, the system ofswitching flow of an inactive gas and flow of a precursor gasillustrated in FIG. 1B (described earlier) can be used to introduce theprecursor gas in pulses without substantially fluctuating pressure ofthe reaction chamber.

A skilled artisan will appreciate that the apparatus includes one ormore controller(s) (not shown) programmed or otherwise configured tocause the deposition and reactor cleaning processes described elsewhereherein to be conducted. The controller(s) are communicated with thevarious power sources, heating systems, pumps, robotics, and gas flowcontrollers, or valves of the reactor, as will be appreciated by theskilled artisan.

In some embodiments, a dual chamber reactor (two sections orcompartments for processing wafers disposed close to each other) can beused, wherein a reactant gas and a noble gas can be supplied through ashared line whereas a precursor gas is supplied through unshared lines.

The film having filling capability can be applied to varioussemiconductor devices including, but not limited to, cell isolation in3D cross point memory devices, self-aligned Via, dummy gate (replacementof current poly Si), reverse tone patterning, PC RAM isolation, cut hardmask, and DRAM storage node contact (SNC) isolation.

EXAMPLES

In the following examples where conditions and/or structures are notspecified, the skilled artisan in the art can readily provide suchconditions and/or structures, in view of the present disclosure, as amatter of routine experimentation. A skilled artisan will appreciatethat the apparatus used in the examples included one or morecontroller(s) (not shown) programmed or otherwise configured to causethe deposition and reactor cleaning processes described elsewhere hereinto be conducted. The controller(s) were communicated with the variouspower sources, heating systems, pumps, robotics and gas flow controllersor valves of the reactor, as will be appreciated by the skilled artisan.

Reference Example 1 (FIG. 3)

An amorphous carbon polymer film was deposited on a Si substrate (havinga diameter of 300 mm and a thickness of 0.7 mm) having trenches with anopening of approximately 25 to 35 nm, which had a depth of approximately85 nm (an aspect ratio was approximately 2.4 to 3.4), by PEALD-likeprocess in a bottom-up manner according to the process sequence shown inFIG. 12 under the conditions shown in Table 2 below using the apparatusillustrated in FIG. 1A and a gas supply system (FPS) illustrated in FIG.1B. The films were deposited to fully fill the trenches and furtheraccumulate thereon, forming a planar top surface. PEALD-like cycles wererepeated 242 times (p=242). Thereafter, aching was continuouslyconducted using a mixture of O₂ and Ar or a mixture of N₂ and H₂according to the process sequence shown in FIG. 12 under the conditionsshown in Table 2 below.

TABLE 2 (numbers are approximate) Temp. SUS temp (° C.). 75 setting SHDtemp (° C.) 50 Wall temp (° C.) 75 BLT temp (° C.) RT Depo Pressure (Pa)1160 Gap (mm) 16.5 Feed time (s) 0.4 Purge (s) 0.1 RF time (s) 1.5 Purge(s) 0.1 RF power (W) 230 Precursor Cyclopentene Carrier He Carrier flow(slm) 0.1 Dry He (slm) 0.2 Seal He (slm) 0.1 Ashing Stabilization (s).15 Purge (s) 10 RF time (s) 10-300 RF power (W) 50-200 Ashing gas O₂/Ar(slm) 0.5/0.5 Ashing gas N₂/H₂ (slm) 0.5/0.5

FIG. 3 shows STEM photographs of cross-sectional views of the trenchessubjected to bottom-up deposition in (a), followed by O₂/Ar ashing in(b) or by N₂/H₂ ashing in (c). As shown in FIG. 3, it was confirmed thatthe amorphous carbon polymer film was effectively flowable and fullyfilled all the trenches (regardless of the size differences) and furtheraccumulated thereon, forming a planar top surface, and by the ashingprocess, the amorphous carbon polymer film could fully be removed orached without degrading CD integrity, i.e., by manipulating the ashingtime, a desired amount of amorphous carbon polymer film can be removedwithout degrading CD integrity.

Example 1

An amorphous carbon polymer film was deposited on a Si substrate (havinga diameter of 300 mm and a thickness of 0.7 mm) having trenches with anopening of approximately 20 nm, which had a depth of approximately 200nm (an aspect ratio was approximately 10), by PEALD-like process in abottom-up manner under the same conditions as in Reference Example 1except that the deposition cycle was repeated 210 times (p=210) so thatthe film accumulated on the top surface of the substrate to a thicknessof 100 nm. Thereafter, ashing was continuously conducted using a mixtureof O₂ and Ar in the same manner as in Reference Example 1 except that RFtime was shortened to 90 seconds so as to form film structures havingbottom-only topology wherein the film was ashed to a depth of 181 nmfrom the top surface of the substrate.

FIG. 9 shows STEM photographs of cross-sectional views of the trenchessubjected to the bottom-up deposition, wherein (a) represents trenchesat completion of deposition, and (b) represents the trenches afterashing. As shown in FIG. 9, it was confirmed that the amorphous carbonpolymer film was effectively flowable and fully filled all the trenchesand further accumulated thereon, forming a planar top surface, and bythe ashing process, the amorphous carbon polymer film could be removedor ashed uniformly in all the trenches without degrading CD integrity,forming homogenous film structures having uniform bottom-only topology.

Example 2

An amorphous carbon polymer film was deposited on a Si substrate havingtrenches in the same manner as in Example 1 except that ashing timevaried.

FIG. 10 shows STEM photographs of cross-sectional views of the trenchessubjected to bottom-up deposition (full fill), wherein raw (a)represents a mixture of wide trenches and narrow trenches havingdifferent widths (the scale represents 300 nm), raw (b) representsintermediate trenches (the scale represents 60 nm), and raw (c)represents wide trenches with slight difference in width (the scalerepresents 60 nm), column (1) represents the trenches with full-filldeposition (210 cycles of deposition) prior to ashing, column (2)represents the trenches after ashing for 105 seconds, column (3)represents the trenches after ashing for 129 seconds, and column (4)represents the trenches after ashing for 165 seconds.

FIG. 11 shows STEM photographs of cross-sectional views of the trenchessubjected to bottom-up deposition, wherein (a) represents trenches atcompletion of full-fill deposition (210 cycles of deposition), (b)represents the trenches after ashing for 240 seconds, and (c) representsthe trenches after ashing for 300 seconds.

As shown in FIGS. 10 and 11, it was confirmed that the amorphous carbonpolymer film was effectively flowable and fully filled all the trenchesand further accumulated thereon, forming a planar top surface, and bythe ashing process, the amorphous carbon polymer film could be removedor ached uniformly in all the trenches without degrading CD integrity,forming homogenous film structures having uniform bottom-only topology.Also it was confirmed that surprisingly a combination of full-filldeposition and ashing could homogenously accomplish bottom-onlydeposition substantially without the loading effect.

Reference Example 2

An amorphous carbon polymer film was deposited on a Si substrate (havinga diameter of 300 mm and a thickness of 0.7 mm) having trenches with anopening of approximately 150 nm, which had a depth of approximately 2500nm (an aspect ratio was approximately 17), by PEALD-like process in abottomless manner under the same conditions as in Reference Example 1except that the deposition cycle was repeated 350 times (p=350) so thatthe film accumulated on the top surface of the substrate to a thicknessof 160 nm.

The bottomless deposition has been confirmed by STEM photographs ofcross-sectional views of trenches subjected to the bottomlessdeposition, which include (a) a view of a series of the film-depositedtrenches, (b) an enlarged view of a top portion of one of the trenches,(c) an enlarged view of a bottom portion of the trench, and (d) anenlarged view of sidewalls of the trench. It has been confirmed thatalthough the trenches are not fully filled with the film as observed in(a), the amorphous carbon polymer film is effectively flowable, whereinalthough the top portion of the trench is closed off with the film (thetop is overfilled) as observed in (b), the film flows downward andextends along the sidewalls of the trench toward the bottom of thetrench as observed in (d), without reaching the bottom of the trench asobserved in (c), forming substantially conformal (substantially uniformthickness along the sidewalls) and homogenous film structures along thesidewalls.

Reference Example 3

An amorphous carbon polymer film was deposited on a Si substrate (havinga diameter of 300 mm and a thickness of 0.7 mm) having trenches with anopening of approximately 140 to 160 nm, which had a depth ofapproximately 2500 nm (an aspect ratio was approximately 16 to 18), byPEALD-like process in a bottomless manner under the same conditions asin Reference Example 1 except that the deposition cycle was repeated 300times (p=300) so that the film accumulated on the top surface of thesubstrate to a thickness of 116 nm.

FIG. 4 shows a schematic illustration of a STEM photograph of across-sectional view of the trench subjected to bottomless deposition(300 cycles) without ashing. As shown in FIG. 4, it was confirmed thatalthough the trenches were not fully filled with the film, the amorphouscarbon polymer film was effectively flowable, wherein although the topportion of the trench was just or barely closed off with the film (thetop was overfilled) and although the film accumulated on the top surfaceof the substrate, the film flowed downward and extended along thesidewalls of the trench toward the bottom of the trench and slightlyreached the bottom of the trench, forming substantially conformal(substantially uniform thickness along the sidewalls) and homogenousfilm structures along the sidewalls. The small deposition of the film atthe bottom does not interfere with further etching to form an ultradeephole, if dry etching conditions are set to have high selectivity(e.g., >100) of carbon film relative to the underlying layer, and thus,this deposition is still referred to as bottomless deposition. Further,by tuning the flowability of the film (slightly reducing theflowability), the flow of the film along the sidewalls can be stoppedbefore reaching the bottom.

Example 3

An amorphous carbon polymer film was deposited on a Si substrate in abottomless manner under the same conditions as in Reference Example 3.Thereafter, ashing was continuously conducted using a mixture of O₂ andAr in the same manner as in Reference Example 1 except that RF time wasshortened to 90 seconds so as to thin a portion of the film accumulatedon the top surface of the substrate and remove a top closed portion(overfilled portion) of the film in the trenches to open the trenches,thereby forming a spacer-like structure in the trenches.

FIG. 5 shows a schematic illustration of a STEM photograph of across-sectional view of the trench subjected to bottomless deposition(300 cycles), followed by ashing (90 seconds). As shown in FIG. 5, itwas confirmed that by ashing, the overfilled top portion of the trenchwas effectively removed so as to open the top of the trench withoutdegrading CD integrity, forming substantially conformal (substantiallyuniform thickness along the sidewalls) and homogenous film structuresalong the sidewalls.

Reference Example 4

An amorphous carbon polymer film was deposited on a Si substrate in abottomless manner under the same conditions as in Reference Example 3except that the deposition cycle was repeated 350 times (p=350) so thatthe film accumulated on the top surface of the substrate to a thicknessof 160 nm and completely closed the top opening of the trenches (thethickness of the overfilled portion above the trenches was 145 nm).

FIG. 6 shows a schematic illustration of a STEM photograph of across-sectional view of the trench subjected to bottomless deposition(350 cycles) without ashing. As shown in FIG. 6, it was confirmed thatalthough the trench was not fully filled with the film, the amorphouscarbon polymer film was effectively flowable, wherein although the topportion of the trench was closed off with the film and although the filmaccumulated on the top surface of the substrate, the film floweddownward and extended along the sidewalls of the trench toward thebottom of the trench in a manner similar to that in Reference Example 3.

Example 4

An amorphous carbon polymer film was deposited on a Si substrate in abottomless manner under the same conditions as in Reference Example 4.Thereafter, ashing was continuously conducted using a mixture of O₂ andAr in the same manner as in Reference Example 1 except that RF time wasshortened to 90 seconds so as to thin a portion of the film accumulatedon the top surface of the substrate and remove a top closed portion(overfilled portion) of the film in the trenches to open the trenches,thereby forming a spacer-like structure in the trenches (the thicknessof the overfilled portion above the trenches was 95 nm).

FIG. 7 shows a schematic illustration of a STEM photograph of across-sectional view of the trench subjected to bottomless deposition(350 cycles), followed by ashing (90 seconds). As shown in FIG. 7, itwas confirmed that by ashing, the overfilled top portion of the trenchwas effectively removed so as to open the top of each trench withoutdegrading CD integrity, forming substantially conformal (substantiallyuniform thickness along the sidewalls) and homogenous film structuresalong the sidewalls.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention.

We/I claim:
 1. A method of forming a topology-controlled layer on apatterned recess of a substrate, comprising: (i) depositing a Si-freeC-containing film having filling capability on the patterned recess ofthe substrate by pulse plasma-assisted deposition to fill the recess ina bottom-up manner or bottomless manner; and (ii) subjecting thebottom-up or bottomless film filled in the recess to plasma ashing toremove a top portion of the filled film in a manner leaving primarily orsubstantially only a bottom portion of the filled film or primarily orsubstantially only a sidewall portion of the filled film.
 2. The methodaccording to claim 1, wherein the plasma ashing in step (ii) isconducted using a direct or remote oxygen or hydrogen plasma.
 3. Themethod according to claim 2, wherein the direct or remote oxygen orhydrogen plasma is a direct or remote plasma of gas(es) selected fromthe group consisting of solely H₂, a mixture of Ar and H₂, a mixture ofN₂ and H₂, a mixture of He and H₂, solely O₂, a mixture of O₂ and Ar, amixture of O₂ and He, a mixture of O₂ and N₂.
 4. The method according toclaim 1, wherein in step (i), the Si-free C-containing film is depositedusing a hydrocarbon precursor.
 5. The method according to claim 1,wherein step (i) comprises: (ia) supplying a precursor to a reactionspace where the substrate is placed, and (ib) exposing the patternedrecess of the substrate to a plasma to deposit the Si-free C-containingfilm in the patterned recess, wherein step (ib) is conductedintermittently in a manner pulsing the plasma, and step (ia) isconducted continuously or intermittently without overlapping step (ib)as a step prerequisite for step (ib).
 6. The method according to claim1, wherein the Si-free C-containing film is constituted substantially byhydrocarbons.
 7. The method according to claim 1, wherein an aspectratio of the recess is in a range of 10 to 100, and a depth of therecess is more than 200 nm wherein the recess is filled with the film ina bottomless manner in step (i) and a top portion of the filled filmcloses a top opening of the recess.
 8. The method according to claim 6,wherein plasma ashing is conducted to open the closed top portion of therecess and to leave primarily or substantially only the sidewall portionof the filled film in step (ii).
 9. The method according to claim 1,wherein the substrate has multiple recesses having aspect ratios of 2 to30 wherein the recesses are filled with the film in a bottom-up mannerin step (i) wherein there are variations in surface topology due to theloading effect.
 10. The method according to claim 8, wherein step (i)continues until planarization of the film above the multiple recessesoccurs, and plasma ashing is then conducted to make the surface topologyof the film filled in the multiple recesses uniform, and to leaveprimarily or substantially only the bottom portion of the filled film instep (ii).